Longtime NBA big man Nick Collison announced his retirement from the league Thursday. The 37-year-old entered the NBA in the historic 2003 draft class featuring LeBron James, Dwyane Wade, Carmelo Anthony and Chris Bosh, and now he’s calling it quits after 15 years.

“I started in cold gyms in small towns in Iowa and ended up playing in more than 1,000 games over 15 years in the best league in the world,” Collison wrote in an article published by ESPN Thursday. “I’ve had an incredible run. I’m proud of my career … But it’s time to go. I’m retiring from competitive basketball.”

Known throughout his career as a beloved teammate and locker room presence, Collison played his entire career for one franchise. He started with the Seattle SuperSonics back in 2003 (although he didn’t make his debut until 2004 due to an injury), then stuck with the team for a decade after its move to Oklahoma City in 2008.

Collison’s best statistical season came in 2007-08, when he recorded 9.8 points and 9.4 rebounds per game for a dreadful Sonics team that went 20-62. He would continue to be a key role player for the Thunder during their rise to contention under Kevin Durant and Russell Westbrook. As a result, Collison played in 91 playoff games, including the 2012 NBA Finals against the Heat.

He finishes his career with per-game averages of 5.9 points on 53 percent shooting and 5.2 rebounds per game.